在做电商项目的时候，会遇到要对订单明细进行纳税金额拆分，即将税额拆分到每个商品上，明确商品的税额，本文记录实现方案，方便备查。
案例数据
本案例模拟的相关数据
订单金额为100元【10000分】，税率为5%，即税额为5元【500分】
| 订单总金额【含税】 payAmount | 订单税额 rateAmount |
|---|---|
| 100 | 3 |
商品数量，总数量为8个，包含3个商品，下表是各商品的数量。
| 商品信息 | 个数 |
|---|---|
| 总数量 | 8 |
| 商品1 | 4 |
| 商品2 | 3 |
| 商品3 | 1 |
实现思路
1、计算出平均金额
即商品平均金额，税额平均金额，注意要向下取整，保证最后的金额不为负数。
| 类型 | 金额 |
|---|---|
| 商品平均金额【订单金额/商品数量】 | 10000/8=1250 |
| 税额平均金额【税额/商品数量】 | 500/8=62 |
2、计算每个商品的金额
分为两种计算方式，
前n-1个商品计算方式：即计算每个商品的金额，税额，不含税金额，公式为 上一步计算的各项平均数，乘于商品数量，如商品1如下表所示。
| 类型 | 金额 |
|---|---|
| 商品1金额【平均订单金额*商品数量】 | 1250*4=5000 |
| 商品1税额【税额平均金额*商品数量】 | 62*4=248 |
第n个商品计算方式：总的金额 减去 前n-1个商品累计的金额。
实现方案
1、订单 order 实体
order 实体，订单级别的字段，包含商品总数，支付总金额等
import java.io.Serializable;
import java.util.List;
@Data
public class Order implements Serializable{
/**
* 序列号
*/
private static final long serialVersionUID = 6652550451095312169L;
/**
* 订单号
*/
private String orderNo;
/**
* 支付金额
*/
private Long payAmount;
/**
* 税额
*/
private Long rateAmount;
/**
* 商品数量
*/
private Long skuNum;
/**
* 非含税金额
*/
private Long taxtedAmount;
/**
* 明细集合
*/
private List<OrderDetail> orderDetailList;
}
2、订单明细 orderDetail 实体
orderDetail 实体，订单明细级别的字段，包含商品明细，商品名称，商品数量等
import java.io.Serializable;
@Data
public class OrderDetail implements Serializable{
/**
* 序列号
*/
private static final long serialVersionUID = 7157867993602926767L;
/**
* 订单号
*/
private String orderNo;
/**
* 明细ID
*/
private String detailId;
/**
* 商品名称
*/
private String skuName;
/**
* 支付金额
*/
private Long payAmount;
/**
* 税额
*/
private Long rateAmount;
/**
* 非含税金额
*/
private Long taxtedAmount;
/**
* 商品数量
*/
private Long skuNum;
}
3、实现类
定义主体方法，实现税额和不含税金额的拆分
static List<OrderDetail> SplitOrderDetailTest(Order order) {
System.out.println("进入拆分SplitOrderDetail方法,入参order为:" + order);
List<OrderDetail> detailList = order.getOrderDetailList();
// 商品金额
long amount = order.getPayAmount();
// 税额
long rateAmount = order.getRateAmount();
// 明细数量
long skuNum = order.getSkuNum();
// 平均商品成本金额,向下取整
long aveAmount = (long) Math.floor(amount / skuNum);
// 平均商品税额金额，向下取整
long aveRateAmount = (long) Math.floor(rateAmount / skuNum);
// 平均商品不含税金额【平均商品金额-平均商品税额金额】
long aveNoRateAmount = aveAmount - aveRateAmount;
System.out
.println("计算完毕的rateAmount为:" + rateAmount + ",amount为:" + amount + ",skuNum为:" + skuNum + ",aveAmount为"
+ aveAmount + ",aveRateAmount为:" + aveRateAmount + ",aveNoRateAmount为:" + aveNoRateAmount);
// 累计拆分完 金额
long detailSumAmount = 0l;
// 累计拆分完 税额
long rateSumAmount = 0l;
// 累计拆分完 不含税金额
long taxedSumAmount = 0l;
System.out.println("当前detailList.size()为:" + detailList.size());
for (int i=0; i < detailList.size()-1;i++) {
System.out.println("当前遍历的detail为:" + JSON.toJSONString(detailList.get(i)));
OrderDetail orderFinallyDetail = new OrderDetail();
BeanUtils.copyProperties(detailList.get(i),orderFinallyDetail);
if ( i < detailList.size()-1) {
System.out.println("进入循环内:" + JSON.toJSONString(i));
// 拆分完 金额【平均金额*商品数量】
long detailAmount = aveAmount * detailList.get(i).getSkuNum();
detailSumAmount = detailSumAmount + detailAmount;
System.out.println("计算拆分完的金额detailAmount为:" + detailAmount + ",detailSumAmount为" + detailSumAmount);
// 拆分完 税额【平均税额*商品数量】
long rateDetailAmount = aveRateAmount * detailList.get(i).getSkuNum();
rateSumAmount = rateSumAmount + rateDetailAmount;
System.out.println("计算税额的rateDetailAmount为:" + rateDetailAmount + ",rateSumAmount为" + rateSumAmount);
orderFinallyDetail.setRateAmount(rateDetailAmount);
// 不含税金额【本成本拆分完金额 - 本成本拆分完税额】
long taxedAmount = detailAmount - rateDetailAmount;
taxedSumAmount = taxedSumAmount + taxedAmount;
System.out.println("计算不含税税额的taxedAmount为:" + taxedAmount + ",taxedSumAmount为" + taxedSumAmount);
orderFinallyDetail.setTaxtedAmount(taxedAmount);
}
// list末位采用倒挤方式取值
else {
// 末位税额【总税额-累计扣除的税额】
long taxAmount = rateAmount - rateSumAmount;
System.out.println("计算末位倒挤税额的taxAmount为:" + taxAmount);
orderFinallyDetail.setRateAmount(taxAmount);
// 末位不含税金额【(总金额-税额)-累计扣除的不含税金额】
long taxedAmount = (amount - rateAmount) - taxedSumAmount;
System.out.println("计算末位倒挤不含税税额的taxedAmount为:" + taxedAmount);
orderFinallyDetail.setTaxtedAmount(taxedAmount);
}
System.out.println("保存的orderFinallyDetail的信息为:" + JSON.toJSONString(orderFinallyDetail));
detailList.add(orderFinallyDetail);
}
return detailList;
}
4、测试启动
模拟数据，调用方法
public static void main(String[] args) {
Order order = new Order();
order.setOrderNo("12345678");
order.setSkuNum(8L);
order.setPayAmount(10000L);
order.setRateAmount(500L);
List<OrderDetail> detailList = new ArrayList<>();
// 商品1
OrderDetail detailOne = new OrderDetail();
detailOne.setDetailId("1111");
detailOne.setOrderNo("12345678");
detailOne.setSkuNum(4L);
detailOne.setSkuName("商品1");
detailList.add(detailOne);
// 商品2
OrderDetail detailTwo = new OrderDetail();
detailTwo.setDetailId("2222");
detailTwo.setOrderNo("12345678");
detailTwo.setSkuNum(3L);
detailTwo.setSkuName("商品2");
detailList.add(detailTwo);
// 商品3
OrderDetail detailThree = new OrderDetail();
detailThree.setDetailId("3333");
detailThree.setOrderNo("12345678");
detailThree.setSkuNum(1L);
detailThree.setSkuName("商品3");
detailList.add(detailThree);
System.out.println("构造的detailList的信息为:" + JSON.toJSONString(detailList));
order.setOrderDetailList(detailList);
List<OrderDetail> detailFinallyList = SplitOrderDetailTest(order);
System.out.println("拆分完的detailFinallyList明细信息为:" + JSON.toJSONString(detailFinallyList));
}
5、实现结果
拆分结果如下所示。
{"detailId":"1111","orderNo":"12345678","rateAmount":248,"skuName":"商品1","skuNum":4,"taxtedAmount":4752},
{"detailId":"2222","orderNo":"12345678","rateAmount":186,"skuName":"商品2","skuNum":3,"taxtedAmount":3564},
{"detailId":"3333","orderNo":"12345678","rateAmount":66,"skuName":"商品3","skuNum":1,"taxtedAmount":1184}]
